Toward the decarbonization of industrial drying technologies: Cross-sector sustainability, economics and efficiency integrated assessments with emphasis on the wood and paper Industries

The transition towards a sustainable European economy, driven by policies and initiatives such as the European Climate Law, the EU Taxonomy, the Renewable Energy Directive and the Sustainability Standards, has brought sustainability to the forefront across multiple industrial sectors. Energy-intensive processes, such as drying technologies, play a key role due to their substantial contribution to environmental burdens. In sectors such as wood and paper, the drying stage accounts for approximately 50–70% and 60–80% of the total energy consumption of the process, respectively. With the aim of moving towards more efficient drying technologies and more sustainable processes, this critical review provides an in-depth analysis of the drying technologies commonly used in these sectors. The objective is to evaluate their energy performance by considering specific energy consumption (SEC) and energy efficiency as representative parameters in energy-intensive processes. To ensure compliance with environmental and economic objectives, it is essential to implement robust and comprehensive assessment methodologies. Accordingly, this review also examines the application of Life Cycle Assessment (LCA) and Techno-Economic Analysis (TEA) methodologies to validate environmental and economic performance. For the wood sector, kiln dryers are the most common, with an SEC of 3.80 MJ/kg_ev,_water, while heat pump dryers show the greatest sustainability potential with an SEC of 2.39 MJ/kg_ev,_water. In the paper industry, multi-cylinder dryers are the most widely used, showing a medium SEC value (around 3.3 MJ/kg_ev,_water) and high efficiency, around 75%. On the other hand, in the case of sustainability analysis, it can be concluded that the integration of LCA and TEA methodologies remains largely unexplored, with only 10 and 11out of the 59 articles analyzed applying each approach, respectively. Few LCA studies have included the drying stage within the system boundaries, and there is a clear lack of harmonization between the analyses. Therefore, future studies should integrate the development of more efficient drying technologies with comprehensive sustainability assessments to ensure their technical, economic and environmental viability. Greater effort is also needed to unify terminology and methodological approaches, thus facilitating comparison between technologies.